linux-kernel - [tip: sched/core] PCI: Restrict probe functions to housekeeping CPUs

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Date:   Thu, 09 Jul 2020 08:45:55 -0000
From:   "tip-bot2 for Alex Belits" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Alex Belits <abelits@...vell.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: sched/core] PCI: Restrict probe functions to housekeeping CPUs

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     69a18b18699b59654333651d95f8ca09d01048f8
Gitweb:        https://git.kernel.org/tip/69a18b18699b59654333651d95f8ca09d01048f8
Author:        Alex Belits <abelits@...vell.com>
AuthorDate:    Thu, 25 Jun 2020 18:34:42 -04:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 08 Jul 2020 11:39:01 +02:00

PCI: Restrict probe functions to housekeeping CPUs

pci_call_probe() prevents the nesting of work_on_cpu() for a scenario
where a VF device is probed from work_on_cpu() of the PF.

Replace the cpumask used in pci_call_probe() from all online CPUs to only
housekeeping CPUs. This is to ensure that there are no additional latency
overheads caused due to the pinning of jobs on isolated CPUs.

Signed-off-by: Alex Belits <abelits@...vell.com>
Signed-off-by: Nitesh Narayan Lal <nitesh@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
Link: https://lkml.kernel.org/r/20200625223443.2684-3-nitesh@redhat.com
---
 drivers/pci/pci-driver.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index da6510a..449466f 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/sched/isolation.h>
 #include <linux/cpu.h>
 #include <linux/pm_runtime.h>
 #include <linux/suspend.h>
@@ -333,6 +334,7 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
 			  const struct pci_device_id *id)
 {
 	int error, node, cpu;
+	int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
 	struct drv_dev_and_id ddi = { drv, dev, id };
 
 	/*
@@ -353,7 +355,8 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
 	    pci_physfn_is_probed(dev))
 		cpu = nr_cpu_ids;
 	else
-		cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
+		cpu = cpumask_any_and(cpumask_of_node(node),
+				      housekeeping_cpumask(hk_flags));
 
 	if (cpu < nr_cpu_ids)
 		error = work_on_cpu(cpu, local_pci_probe, &ddi);